Efficient production of the high-intensity natural sweetener siamenoside I by the exo-1,3-beta glucanase (Exo15) from Meyerozyma guilliermondii LHGNSJ-VS01.

The scarcity of siamenoside I (SI) hindered its widespread application. Addressing this challenge, we devised an innovative biocatalytic strategy and biological solution for large-scale SI production. Endo 15, an endophyte from Siraitia grosvenorii, exhibited excellent proficiency in SI synthesis, achieving a remarkable 50.65% SI abundance. By harnessing the extracellular protein of Endo 15 (EP), we further escalated SI abundance to 83.59 ± 2.5%, accompanied by full substrate conversion. Delving into the underlying mechanisms, we identified Exo15, a distinct functional protein derived from EP, displaying merely 48.88% amino acid similarity to the yeast exo-1,3-beta glucanase (Exg1). Successfully overexpressing Exo15 in E. coli, we confirmed its functionality in line with EP. Exo15 exhibited exceptional catalytic prowess, efficiently hydrolyzing mogroside V into the high-potency sweetener SI, with unparalleled activity and specificity. Our groundbreaking approach yielded an impressive SI titer of 54 g/L, coupled with an average conversion rate of 2.5 g/L per hour. These outstanding outcomes underscore the immense potential of Exo15 in cost-effective industrial production of the premium natural sweetener, siamenoside I, paving the way for its widespread adoption.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-025-04260-2.